We have been studying the cell cycle of E. coli to determine how cells coordinate a complex series of events. We have identified four loci that, when mutated, lead to an increase in chromosome number. The locus that we have been concentrating on, mbrA, is involved in counting chromosomes. Our focus has been to characterize mbrA using molecular biological and genetic techniques. To identify other players in chromosome counting, we have identified interactive suppressors of the mbrA mutants. A second approach to chromosome counting that we have undertaken is to determine the mechanism of action of our original selection, resistance to camphor vapors. Selection for overproduction of wild-type genes that lead to camphor resistance yielded three additional genes. One of these, mbrE, may be identical to cspE, which has been implicated in the regulation of chromosome biology. Thus, all of our genes have some tie to how chromosomes are replicated, counted, divided or moved to daughter cells. Our studies on bacterial chromosome biology will allow us to understand how bacteria accomplish this very fundamental process.